## 4pSP4. Tomographic reconstruction techniques for pulse-echo imaging.

### Session: Thursday Afternoon, December 5

### Time: 2:50

**Author: I. Akiyama**

**Location: Dept. of Elect. Eng., Shonan Inst. of Technol., Fujisama, Japan**

**Abstract:**

Imaging is possible based on tomographic reconstruction techniques such as
computed tomography, although ultrasonic pulse echo imaging is based on focusing
techniques. It is possible to obtain three-dimensional imaging data by the
tomographic method. When divergent waves are insonified toward a target by a
part of a spherical surface, backscattered waves which are generated at the
target are received by the transducer, and the echo signal on a delayed time is
expressed as the integral of scattered waves at the surface of the radius
proportional to the delay. If the transducer has both convex and concave parts
of the spherical surface, both divergent waves and convergent waves can be
generated. These waves are focused onto the arc on the spherical surface; thus
the amplitude at the delay of the received echoes is expressed as the product of
the backscatter coefficient on the arc and the diffraction term. Those values
are equivalent to the projection data as the tomographic reconstruction
technique. Therefore the distributions of the backscatter coefficient on the
spherical surface are reconstructed from the projection of the echoes. In this
study the effects of the angle dependency of the amplitude on the spherical
surface due to the diffraction term are discussed and then the method for
correction is described.

ASA 132nd meeting - Hawaii, December 1996